The present invention relates to a high speed molecular driver for transferring preferred momenta to gaseous molecules and to molecular momentum transfer devices constructed therewith. One exemplary use of the invention may be as a molecular vacuum pump for evacuating a chamber.
Presently known molecular momentum transfer devices include turbo molecular axial and radical flow pumps, molecular drag pumps and ejector and diffusion working fluid pumps.
All of the foregoing devices operate to move molecules by striking the same with one or more rotating elements or with a linear velocity set of solid or fluid elements; however, they all suffer from various drawbacks and deficiencies. One such deficiency of rotating devices is the high construction cost of the parts of such devices making them expensive, both to produce and maintain. Conventional molecular momentum transfer devices are also relatively heavy and bulky and consume a large amount of physical area and space. This also severely limits their mounting flexibility, for example, to a chamber containing a gas to be evacuated. The rotor structures of conventional molecular momentum transfer devices and the housing around them are also quite heavy. The strength to density ratio of the heavy rotor structure is a limiting factor on the achievable tip velocity of the rotating elements and considerable energy is stored therein during operation which may cause extensive damage if released, for example, by component breakage. In addition, the relatively heavy and bulky rotor structures require considerable driving and suspension structures which further limits obtainable tip velocity. An additional drawback to conventional momentum transfer devices is the considerable energy required to start, maintain and/or stop the rotating structures or to drive the working fluid of diffusion or ejector devices. A relatively low molecular transfer efficiency is also commonplace, especially for low molecular weight molecules because the driving velocity of the moving elements is too low.
One object of the present invvention is to overcome the above problems by providing a unique fiber array molecular driver and a molecular momentum transfer device constructed therewith having a rotor structure which is cheaper to manufacture and maintain, has a lower mass, requires less space, obtains a higher rotor tip velocity and which requires less energy in operation and construction and stores less energy when operating.
An additional object of the invention is to provide a fiber array molecular driver and a molecular momentum transfer device constructed therewith having a unique rotor structure which more assuredly directs molecules struck by the moving rotor to a predetermined direction, thus facilitating collection or removal of struck molecules and increasing the molecular transfer efficiency.
An additional object of the invention is to provide a fiber array molecular driver and a molecular momentum transfer device constructed therewith having a unique rotor structure which can be used in a variety of applications including a molecular pump, a thin film molecular coating device, a molecular separator, or a molecular reactor.
An additional object of the invention is to provide a fiber array molecular driver and a molecular momentum transfer device constructed therewith which requires lower energy for suspension and rotation of the rotor, makes the spacing between the rotor and suspension and rotation structures less critical and which can easily obtain a rotor tip speed which is higher than the average molecular speed of molecules colliding with the rotor.
These and other objects and advantages of the invention are achieved with a fiber array molecular driver and a molecular momentum device constructed therewith having a rotor structure comprising a central hub and an array of fine fibers attached to the hub which, during rotation at operating speed, stand radially outward of the hub at an angle normal thereto. The rotor is magnetically suspended and driven and may be used alone or with other like rotors and/or stationary structures to provide a molecular pump, a molecular gas separator, a coating apparatus for a substrate, or a reaction device wherein gas molecules are directed towards one another for collision.
At operating speed, the tip speed of the fiber array is greater than the average thermal velocity of the molecules which collide therewith such that preferred directional momenta are imparted to the struck molecules. The struck molecules leave the fibers with a distribution in a direction confined to a relatively narrow angle radially outward from the hub which is centered about and peaks around lines normal to the surface of the sides of the fiber tips in the direction of fiber rotation at each point of collision. This facilitates collection of the struck molecules and improves overall operating efficiency of the molecular momentum transfer device.
Additional objects and advantages of the unique fiber array molecular driver and molecular momentum transfer devices constructed therewith of the structure of the invention can be seen from the following detailed description thereof which is taken in conjunction with the accompanying drawings.